Orion Upgrade - 403 Forbidden Errors

I completed an upgrade from Orion 8.5 to 8.5.1, and added SP2. Now I get the following error when I log in:

Orion Website Error

An error has occurred with the Orion website.

Additional Information

System.Net.WebException: The remote server returned an error: (403) Forbidden.
   at System.Net.HttpWebRequest.GetResponse()
   at ClassicSiteProxy.Login(HttpContext context, String username, String password)
   at Login.InitiateLogin()
   at Login.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean
includeStagesAfterAsyncPoint)

 I've checked permissions over and over again - the error isn't specific enough for me
to dive in deeper, and so far, Solarwinds support has been useless.

Any ideas? I'm running this on my Application Server, which has a few other websites
on it, and I'm using host header values to separate the sites. It was working fine in this
same config before the upgrade - I need my Solarwinds back!

Have you seen the following posts? Not quite the same error, but it could be related.

 http://thwack.com/forums/p/5912/25537.aspx#25537

http://thwack.com/forums/p/5727/25617.aspx#25617

THANK YOU!!! I don't know how I missed it...

 In case anyone else has this issue, this post is the key:

 http://thwack.com/forums/p/5912/25537.aspx#25537

You have to just remove the custom.config file in the Inet\Solarwinds\Orion folder. Theres a very good explanation in the afformentioned post. 8.5 (Post-August releases) appears to handle pages differently as far as IIS config is concerned.

 Needless - I'm back up! Thanks again!